How to instantiate I2C devices from the userspace

In general, the kernel should know which I2C devices are connected and
what addresses they live at. However, in certain cases, it does not, so a
sysfs interface was added to let the user provide the information. This
interface is made of 2 attribute files which are created in every I2C bus
directory: new_device and delete_device. Both files are write only and you
must write the right parameters to them in order to properly instantiate,
respectively delete, an I2C device.

File new_device takes 2 parameters: the name of the I2C device (a string)
and the address of the I2C device (a number, typically expressed in
hexadecimal starting with 0x, but can also be expressed in decimal.)

File delete_device takes a single parameter: the address of the I2C
device. As no two devices can live at the same address on a given I2C
segment, the address is sufficient to uniquely identify the device to be
deleted.

Example:
echo eeprom 0x50 > /sys/bus/i2c/devices/i2c-3/new_device

While this interface should only be used when in-kernel device declaration
can't be done, there is a variety of cases where it can be helpful:

• The I2C driver usually detects devices (method 3 above) but the bus
  segment your device lives on doesn't have the proper class bit set and
  thus detection doesn't trigger.
• The I2C driver usually detects devices, but your device lives at an
  unexpected address.
• The I2C driver usually detects devices, but your device is not detected,
  either because the detection routine is too strict, or because your
  device is not officially supported yet but you know it is compatible.
• You are developing a driver on a test board, where you soldered the I2C
  device yourself.

This interface is a replacement for the force_* module parameters some I2C
drivers implement. Being implemented in i2c-core rather than in each
device driver individually, it is much more efficient, and also has the
advantage that you do not have to reload the driver to change a setting.
You can also instantiate the device before the driver is loaded or even
available, and you don't need to know what driver the device needs.

Taken from the Linux kernel documentation.

Considering this, we could instantiate a sensor (hih6130) connected to i2c-1 and with address 0x27 doing:

echo hih6130 0x27 > /sys/bus/i2c/devices/i2c-1/new_device

After that, the device will be available under /sys/bus/i2c/drivers/hih6130/1-0027.

To remove the device you can use:

echo 0x27 > /sys/bus/i2c/devices/i2c-1/delete_device